1. Field of the Invention
The present invention relates to a front plate for a field-emission display.
2. Description of the Related Art
Generally, a field-emission display panel (FED panel) includes a back plate (cathode substrate) and a front plate (anode substrate). The back plate has a glass substrate, emitter electrodes, i.e., electron-emitting elements, formed on the glass substrate, an insulating layer formed over the emitter electrodes, and gate electrodes (extraction electrodes) arranged on the insulating layer perpendicularly to the emitter electrodes. The front plate has a glass substrate, anodes formed on the glass substrate, and fluorescent layers formed over the anodes. The back plate and the front plate are set opposite to each other and joined together with spacers held therebetween, and a space between the back plate and the front plate is evacuated. A predetermined voltage is applied across the emitter electrodes and the gate electrodes and, at the same time, a predetermined voltage is applied across the emitter electrodes and the anodes to make the emitter electrodes emit electrons and to make the electrons collide against the anodes. The fluorescent layers emit light to display an image when the electrons collide with the anodes.
In this FED panel, it is necessary to prevent the unnecessary light emission of the fluorescent layers of cells adjacent to those desired to emit light due to the scattering of electrons emitted by the emitter electrodes and the scattering of secondary electrons emitted as a result of bombardment of the anodes by the electrons to make the fluorescent layers emit light. Conductive barriers are formed between the cells of the front plate by forming a pattern of a height on the order of several tens micrometers so as to isolate the cells of the front plate from each other by processing a film of a polyimide resin or the like by photolithography, and coating the pattern with a metal thin film to prevent the electrons and the secondary electrons from scattering for preventing unnecessary light emission.
In the FED panel provided with such barriers in the front plate, the barriers produce a gas when the same are irradiated with an electron beam. Consequently, the vacuum is reduced, the electrodes of the back plate are deteriorated, the fluorescent layers are deteriorated and the reliability of the FED panel is reduced. When forming the fluorescent layers of the front plate by a fluorescent layer forming process, there is a limit to the process temperature because a material forming the barriers has a low heat resistance, only limited fluorescent materials can be used, and fluorescent layers having desired characteristics cannot be formed. The barriers of the electrically insulating polyimide resin or the like must be coated with the metal thin film to prevent charge-up due to bombardment of the same by secondary electrons, which needs a complicated process.
FED panels disclosed in JP-A Nos. Hei 9-73869 and Hei 10-40837 employ metal spacers for spacing the back plate and the front plate. The metal spacers solve problems caused by production of a gas by the conventional polyimide spacers and charge-up. If the spacers are formed in a pattern having parts formed between the cells, the spacers will function also as barriers.
The spacers of each of the FED panels disclosed in JP-A Nos. Hei 9-73869 and Hei 10-40837 are inevitably in contact with both the front and the back plate. Since the spacers are conductive, the spacers must be disposed relative to the front and the back plate so as not to be in contact with the anodes of the front plate, and the gate electrodes and the electron emitting elements of the back plate. Thus it is necessary to form spacer wiring lines connected to the spacers to maintain the spacers at a predetermined potential and to prevent charge-up in addition to the anodes, the gate electrodes and the electron emitting elements, which reduces the degree of freedom of design and makes fabricating process complicated.
Degree of freedom of design will be increased if, for example, the spacer wiring lines are formed on the front plate separately from the anodes, and an insulating layer is formed between the spacers formed on the spacer wiring lines and the gate electrodes of the back plate. However, it is highly possible that breakdown occurs in the insulating layer when a voltage in the range of several hundreds volt to several thousands volts is applied across the gate electrodes of the back plate and the spacer wiring lines. Thus the spacers employed in the prior art FED panels have problems in their practical application.
The present invention has been made in view of the foregoing circumstances and it is therefore an object of the present invention to provide a front plate for a field-emission display, capable of enhancing the reliability of the field-emission display and of being easily fabricated.
According to a first aspect of the present invention, a front plate for a field-emission display includes a transparent substrate, a conductive black matrix provided with a plurality of apertures and formed on one of the surfaces of the transparent substrate, a plurality of barriers formed at predetermined positions on the black matrix, and fluorescent layers formed in the apertures of the black matrix on the transparent substrate, wherein the barriers are formed of a conductive inorganic material.
Preferably, the conductive inorganic material is one of or one of combinations of metals of a metal group including nickel, cobalt, copper, iron, gold, silver, rhodium, palladium, platinum and zinc, one of alloys each of some of the metals of the metal group, or one of or one of combinations of some metal oxides of a metal oxide group including indium-tin oxide, indium-zinc oxide and tin oxide.
Preferably, an intermediate layer is formed between the barriers and the black matrix, and the intermediate layer has a middle thermal or strength characteristic between those of the transparent substrate and the barriers.
Preferably, the barriers contain particles having a coefficient of thermal expansion smaller than that of the conductive inorganic material.
Preferably, the barriers are formed by an electroplating process.
According to a second aspect of the present invention, a front plate for a field-emission display includes a transparent substrate, a plurality of barriers formed at predetermined positions on one of the surfaces of the transparent substrate, and fluorescent layers formed in desired regions in parts, not provided with the barriers, of the transparent substrate, wherein the barriers are formed of a conductive inorganic material, and the barriers are electrically connected by charge dissipating lines.
Preferably, the conductive inorganic material is one of or one of combinations of metals of a metal group including nickel, cobalt, copper, iron, gold, silver, rhodium, palladium, platinum and zinc, one of alloys each of some of the metals of the metal group, or one of or one of combinations of some metal oxides of a metal oxide group including indium-tin oxide, indium-zinc oxide and tin oxide.
Preferably, a conductive intermediate layer is formed between the barriers and the transparent substrate, and the intermediate layer has a middle thermal or strength characteristic between those of the transparent substrate and the barriers.
Preferably, a black matrix is formed between the barriers and the transparent substrate, the black matrix has a plurality of apertures, and the fluorescent layers are formed in the apertures on the transparent substrate.
Preferably, a conductive intermediate layer is formed between the barriers and the black matrix, and the intermediate layer has a middle thermal or strength characteristic between those of the transparent substrate and the barriers.
Preferably, the barriers are formed by an electroless plating process.
Preferably, the barriers are formed by an electroplating process on the intermediate layer.
Preferably, the barriers contain particles having a coefficient of thermal expansion smaller than that of the conductive inorganic material.
Preferably, the barriers have a height in the range of 20 to 100 xcexcm and a width in the range of 10 to 50 xcexcm.